Abstract
This case study investigates the effects of ventilation intervention on measured and perceived indoor air quality (IAQ) in a repaired school where occupants reported IAQ problems. Occupants’ symptoms were suspected to be related to the impurities leaked indoors through the building envelope. The study’s aim was to determine whether a positive pressure of 5–7 Pa prevents the infiltration of harmful chemical and microbiological agents from structures, thus decreasing symptoms and discomfort. Ventilation intervention was conducted in a building section comprising 12 classrooms and was completed with IAQ measurements and occupants’ questionnaires. After intervention, the concentration of total volatile organic compounds (TVOC) and fine particulate matter (PM2.5) decreased, and occupants’ negative perceptions became more moderate compared to those for other parts of the building. The indoor mycobiota differed in species composition from the outdoor mycobiota, and changed remarkably with the intervention, indicating that some species may have emanated from an indoor source before the intervention.
Highlights
The success of moisture- and mold-damaged building repairs depends on many factors
The school was selected in cooperation with Vantaa Real Estate Center in the spring of 2016, based on its repair history and the fact that a reasonable and controllable part of the building could be isolated for implementing the positive pressure intervention without major ventilation system changes in the building
The ventilation intervention was conducted in four phases: (a) airflow rates in the rooms were measured to determine the initial state of the ventilation; (b) the air distribution ductwork was fully balanced by an authorized company; (c) the air handling unit’s supply and extract fan speeds were adjusted to generate the desired 5–7 Pa positive pressure over the building envelope in each classroom; and (d) airflow rates in the rooms were re-measured, and pressure differences over the envelope were monitored during the entire set-up
Summary
The success of moisture- and mold-damaged building repairs depends on many factors. Reaching a consensus about the necessary repair methods and schedule is not always simple, and the response to problems might be delayed. In well-ventilated buildings, the indoor air is often dry, and school buildings are typically occupied only during normal office hours In such buildings, the risk for condensation is improbable despite the pressure conditions. Our main hypothesis is that positive pressure differences across the building envelope could prevent the infiltration of harmful chemical and microbiological agents into the indoor air of damaged structures, decreasing occupants’ perceptions of symptoms and discomfort. The aims of our research project were to determine the effects of significant ventilation system changes on measured and perceived IAQ in a school building with unsolved indoor air-related problems, and to provide information about the applicability of moderate positive pressure in a well-ventilated building awaiting repairs. IAQ measurements, as well as occupant questionnaires, were conducted before and after ventilation system intervention
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